Electrochemical test strips are designed to measure the concentration of an analyte, such as glucose, in a body fluid sample. In the case of the measurement of glucose in a blood sample, the glucose measurement is based on the selective oxidation of glucose, as for example, by the glucose oxidase enzyme. The glucose is oxidized to gluconic acid by the oxidized form of glucose oxidase and the oxidized enzyme is converted to its reduced state. Next, the reduced enzyme is re-oxidized by reaction with a mediator, such as ferricyanide. During this re-oxidation, the ferricyanide mediator is reduced to ferrocyanide.
When these reactions are conducted with a test voltage applied between two electrodes, a test current is created by the electrochemical re-oxidation of the reduced mediator at the electrode surface. Since, in an ideal environment, the amount of reduced mediator created during the chemical reaction is directly proportional to the amount of glucose in the sample positioned between the electrodes, the test current generated is proportional to the glucose content of the sample.
Test meters that use this principle enable an individual to sample and test a blood sample and determine the blood's glucose concentration at any given time. The glucose current generated is detected by the test meter and converted into a glucose concentration reading using an algorithm that relates the test current to a glucose concentration via a simple mathematical formula. In general, the test meters work in conjunction with a disposable test strip that may include a sample-receiving chamber and at least two electrodes disposed within the sample-receiving chamber in addition to the enzyme and the mediator.
Such a glucose test using a test meter and strip use batch calibration information about the test strip, such as batch slope and intercept values, determined from the manufacturing of a particular strip lot, or batch. When a user performs a glucose test using a strip from a particular strip lot, the batch slope and batch intercept information must be inputted into a test meter in the form of a calibration code by the user if the information varies batch-to-batch. If a user forgets to account for a change in calibration factors when using a different lot of test strips, there is a possibility that an inaccurate glucose measurement result may occur. Such an error can lead to insulin dose errors by the individual resulting in a hypo- or hyperglycemic episode.
To overcome this disadvantage of using test strips, test strip manufacturers have developed test strips and methods of manufacturing the strips, in which test strip lots can be prepared that do not require a user to input any calibration information before performing a test measurement because a high percentage of test strip lots can be produced that have a relatively constant batch slope and batch intercept. Thus, the test strip lots effectively have the same calibration and, when the test strips are used in a glucose test meter manufactured with the calibration information, no calibration coding is necessary or required of the user during each usage of the test strips.